1. Field of the Invention
An aspect of the present invention relates to an electro photographic apparatus such as a copier or a printer that uses electro photographic technology, and more particularly, to a fixing device capable of preventing damage of an end portion thereof and an electro photographic apparatus using the same.
2. Description of the Related Art
As a fixing device of an electro photographic apparatus, a belt fixing device in which an endless belt is provided to heat and melt a toner image is used (for example, see JP-2005-055469-A), and accordingly, a warming-up time can be shortened and a power consumption can be lowered. When a fixing process is performed by using the endless belt, there is a problem that the endless belt moves in a direction perpendicular to the rotation direction thereof, that is, a shift of the endless belt occurs, as the endless belt rotates.
To prevent the shift of the endless belt, a configuration in which a flange is provided to be brought into contact with the end face of the endless belt is used (for example, see JP-H04-305675-A). In addition, to prevent the shift of the endless belt, a configuration in which a steering roller is provided as a roller, over which the endless belt is suspended (for example, see JP-H10-203674-A and JP-H11-024460-A), is used. In the above-described method, when the endless belt is shifted, the steering roller is tilted by a motor so that an axis thereof is shifted to move and correct the endless belt in the opposite direction of the shifted direction.
However, the above-described general methods have a problem in durability of the belt and costs of parts. First, as in JP-H04-305675-A, when the configuration including the flange brought into contact with the end face of the belt is adapted, the end face of the belt is continuously slid on the flange. Accordingly, the end face of the endless belt is worn away, and thereby the durability is lowered. In addition, when the shifting force of the belt is strong, a depression or a wrinkle is generated in the end face of the belt, and there is a problem that an abnormal noise and damage are generated. Generally, in order to reduce the shifting force of the belt, it is needed to control a difference between left and right peripheral lengths of the belt, a thickness of the belt, and the degree of parallelism of the belt and each roller with high precision. Accordingly, the costs of the parts increase, and it is difficult to reduce the cost of the device.
On the other hand, as in JP-H10-203674-A and JP-H11-024460-A, when the configuration including the steering roller is adapted, a sensor that detects the position of the end face of the belt, a motor that tilts the shaft of the roller, a controller that controls the motor based on information detected by the sensor, and the like are needed. Accordingly, the number of parts increases, thereby increasing the size and the cost of the device. In addition, when the shaft of the steering roller is tilted, a wrinkle or a wave shape is generated in the belt due to a difference between tensile forces of the belt on the left and right sides, and accordingly, the durability of the belt is deteriorated.